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Fabian Kislat develops detectors for x-ray and gamma-ray polarimetry in the field of experimental astroparticle physics.

Kislat continues to make major contributions to the development of the balloon-borne x-ray polarimeter X-Calibur. The instrument is scheduled for launch in the 2018/19 Antarctic summer season for a long-duration flight from McMurdo, Antarctica. X-ray polarimetry promises to provide geometrical information about objects that are too small to be spatially resolved.

Kislat uses astrophysical observations to test fundamental laws of physics, such as Lorentz and CPT invariance. Signatures of Lorentz violation include an energy and polarization dependence of the speed of light in vacuum. The energy dependence can be constrained by measurements of the arrival time of high-energy photons in instruments such as the Fermi Large Area Telescope, and polarization measurements, not only of x-rays, but also in the optical band can be used to constrain vacuum birefringence. Vacuum birefringence may also occur in very strong magnetic fields, an effect that is predicted by quantum electrodynamics. Broadband x-ray polarization measurements of accretion-powered pulsars provide a very clear signature of this effect due to an interplay of plasma and vacuum effects in the emission region. X-Calibur or a follow-up space-based mission would be ideally suited to provide the first test of this prediction of QED.